Certain of the known processes for preparing aluminum nitride involve heating aluminum metal or an aluminum compound in a non-oxidizing nitrogeneous atmosphere such as nitrogen, hydrazine and ammonia to form the nitride. Reaction of trialkylaluminum and ammonia or other nitrogen hydride to form aluminum nitride is known from U.S. Pat. No. 3,922,475 which discloses preparation of films of nitrides of Group III elements, including Al, by mixing volatile alkyl derivatives of said elements with ammonia or selected alkyl amines, as gases, and pyrolyzing the mixed gases or the solid reaction product, optionally using a carrier gas such as helium. The intermediate reaction product, formulated for ammonia as R.sub.3 M.NH.sub.3 where M is a Group III element and R is alkyl, is sometimes gaseous. The final products are films deposited on insulating or semiconducting substrates.
Japanese Application No. 78-68700 discloses reacting a hexane solution of triethylaluminum with ammonia, heating to evaporate solvent, then heating under vacuum at 1000.degree. to obtain black aluminum nitride. Myakininkov et al., Inorganic Materials (USSR), 10 (10), 1635 (1974) disclose deposition of aluminum nitride films onto silicon semiconducting substrates by gaseous reaction of Al(C.sub.2 H.sub.5).sub.3 and hydrazine with helium as a carrier gas at a temperature in the range 750.degree. to 1000.degree..
Bahr, FIAT, Rev. Ger. Sci., Inorg, Chem. II, 155 (1948) discloses the reaction of trimethylaluminum and ammonia to form a 1:1 adduct which, on heating at gradually higher temperatures, forms dimethylaluminum amide, then polymeric aluminum amides and finally aluminum nitride. Japanese Application No. 54-013,439 discloses the reaction of purified trialkylaluminum with ammonia or a primary or secondary amine in hydrocarbon solution to form an aluminum nitride precursor containing at least one Al-N bond. The precursor is converted to aluminum nitride powder by heating it above 400.degree. C. in the presence of an inert gas, vacuum or ammonia gas.
At a meeting of the Materials Research Society, April 1986, Palo Alto, Calif., Interrante disclosed the stepwise reaction of trialkylaluminum compounds R.sub.3 Al, where R is C.sub.1-4 alkyl, with ammonia to form aluminum nitride. Trimethylaluminum was reacted with ammonia at low temperatures of about -78.degree. C. in a hydrocarbon solvent, to form a 1:1 adduct. The adduct lost methane on heating at or above 70.degree. C. to give dimethylaluminum amide. Heating at 160.degree. to 200.degree. C. lead to further loss of methane to give CH.sub.3 AlNH. Final conversion of RAlNH to AlN powder was achieved by heating at 1000.degree. C.
U.S. Pat. No. 3,352,637 discloses formation of nitrides of Al, B, Si, or Zr by contacting a gaseous chloride of said element with gaseous ammonia in the presence of a heat transfer gas which is H.sub.2, N.sub.2, or Ar, and which has been pre-heated to at least 2500.degree. C., under conditions such that the reactor wall temperature is below 500.degree. C., preferably about 200.degree. C.
Japanese Application No.8722952 discloses preparation of fine, high purity aluminum nitride powder suitable for manufacturing semi-transparent sintered objects, said powder having an average particle diameter not exceeding 2.mu., prepared by reacting alumina with ammonia or N.sub.2 in the presence of carbon.
Japanese Application No. 62-100,405 discloses aluminum nitride powder having particle sizes less than 3.mu. prepared from selected alumina and carbon by firing an aqueous gel thereof in N.sub.2 at 1350.degree. to 1650.degree. C.